In order to facilitate human-computer interaction, a touch display device has been developed. When an operator's finger touches a display surface of the touch display device, a coordinate of the touch point can be determined. However, at present, only the coordinate of the touch point on the two-dimensional plane can be determined, but coordinates of the touch point in the three-dimensional space cannot be determined and thus other functions such as three-dimensional touch control cannot be realized.
Therefore, how to determine the coordinate of the touch point in the three-dimensional space has become a technical problem to be solved urgently in the art.